The present invention relates to a fuel injection system.
A method for forming an ignitable fuel/air mixture is discussed in German Patent No. 196 42 653. An ignitable fuel/air mixture may be formed in the cylinders of internal combustion engines having direct injection in that fuel is injected by an injector into each combustion chamber bounded by a piston, in response to the release of a nozzle orifice as the result of a valve member lifting off from a valve seat that encircles the nozzle orifice. To produce an internal mixture formation that is optimized with respect to consumption and emissions, in every operating point of the entire characteristics map, under all operating conditions of the internal combustion engine, e.g., in stratified operation, the opening stroke (lift) of the valve member and the injection time are variably adjustable.
German Published Patent Application No. 38 08 635 discusses a fuel injection device for the direct injection of fuel into the cylinder of a mixture-compressing internal combustion engine. The fuel injection device includes a fuel injector, which is positioned in the cylinder wall at a distance to the cylinder head and across from the discharge orifice, and an outlet opening, the jet axis of the fuel injector being directed to the region around the spark plug positioned in the cylinder head. The fuel injector includes a magnet-activated valve needle provided with helical grooves to generate a swirl flow of the injection jet. The jet axis of the fuel injector is directed to the ignition point-disposed in the center of the cylinder head.
Moreover, a device for the injection of fuel into the combustion chamber of a mixture-compressing internal combustion engine having external ignition is discussed in U.S. Pat. No. 5,941,207, in which the fuel is injected, in the shape of a cone, into the combustion chamber at a specific initial angle. The injected fuel fills up the combustion chamber in the shape of a cone, the effects of wall wetting being largely suppressed. During the compression phase, a piston having a relatively flat configuration deforms the injected fuel cloud into a spherical shape. The spherical mixture cloud mixes with the supplied air to a negligible degree at most and, while being compressed further, is guided to the spark gap of the spark plug.
German Published Patent Application No. 198 27 219 discusses a fuel injector for an internal combustion engine that includes a disk for adjusting the fuel jet. It is provided with first nozzle orifices configured along a first circle, which is positioned coaxially to a center axis of the valve body. Moreover, second nozzle orifices are provided, which are disposed along a second circle which is positioned coaxially to the center axis and has a larger diameter than that of the first circle. Each hole axis of the second nozzle orifices forms an acute angle with a reference plane that is perpendicular to the center axis of the valve body. The acute angle is smaller than that which is formed by each hole axis of the first nozzle orifices with the reference plane. Therefore, fuel atomizations, which are injected through the first nozzle orifices, may be directed away from the fuel atomizations that are injected through the second nozzle orifices. As a result, the fuel atomizations, injected through the various circles of nozzle orifices, do not interfere with one another.
The methods or devices for the injection of fuel into the combustion chamber of a mixture-compressing internal combustion engine having external ignition discussed in the aforementioned printed publications, are the complicated combustion-chamber geometries that are required in order to mix the injected fuel with the supplied air, to form an ignitable fuel/air mixture and to convey it for ignition to the vicinity of the spark gap of the spark plug. On the one hand, such combustion-chamber geometries are difficult to produce, and, on the other hand, it is impossible to optimize the combustion with regard to the nitrogen-oxide emission and fuel consumption.
Moreover, in most cases, the spark plug is directly exposed to the fuel of the fuel injector. This not only exposes the spark plug to heavy thermal shock loads, but also results in carbon deposits on the spark plug electrodes, thereby considerably limiting the service life of the spark plug. The fuel injector discussed in German Published Patent Application No. 198 27 219 provides that the fuel, injected into the combustion chamber at different injection angles, for the most part, hits the walls of the combustion chamber or the piston, where it cools. For that reason, its combustion is associated with high pollutant emission or the development of soot.
The fuel injection system according to the present invention provides that, due to the special configuration of the fuel injector relative to the combustion chamber, the injection jet is guided in such a manner that the mixture cloud fills up the combustion chamber in an optimal manner.
This may prevent the wetting of the combustion-chamber walls, may allow a low-emission and low-consumption combustion process.
The configuration of the spray-orifice plate of the fuel injector, which produces a mixture cloud that is able to optimally fill up the combustion chamber.
The disk-shaped configuration of the spray-orifice plate is easy to produce and is able to be installed in standard fuel injectors.
A plurality of rows of injection orifices is arranged on the spray-orifice disk, to provide a raster configuration that may be adapted as needed.
The choice of different diameters of the injection orifices provides that, on the one hand, the jet pattern is able to be formed in this manner and, on the other hand, the stoichiometry of the mixture cloud is able to be influenced.
The positioning of the fuel injector relative to the spark plug has the result that the spark plug is not directly exposed to the fuel jet, since the injection jet moves tangentially to the spark plug, thereby extending its service life.